It depends on your activity levels, metabolism, age etc. in general that amount of protein (assuming your diet is consistent) will keep your muscle mass constant and keep your brain functioning well (and other bodily functions - it’s not siloed in its purpose and basically impacts every aspect of your body’s functions . Your body’s processes are not solely reliant on protein but if you don’t have enough your neurotransmission and cognitive function will suffer. If you consume less protein than your base amount for a prolonged time, your body doesn’t have what it needs to maintain core functions and renew and maintain muscle mass. If you don’t consume enough calories overall you’ll find your body will consume its own muscles as a source of energy which is a dangerous metabolic process that can have lasting detrimental effects.

Basically over a short term or one day in a while, not consuming enough protein shouldn’t be an issue, but on a consistent or prolonged timeline, your body just doesn’t have what it needs to maintain itself and you are at risk of longer term impacts to your wellbeing in many facets of your basic bodily functions. I’ve read numbers like .75g per kg for women and .84g per kg for men daily, for basic maintenance of bodily condition. Obviously it isn’t One size fits All, but as a general jumping off point I think that’s a reasonable ballpark. Basically if you’re healthy, and assuming all other things being equal, those amounts should maintain your current state.